Power in Circuits Video Lessons

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# Problem: An automobile starter motor has an equivalent resistance of 0.0500 Ω and is supplied by a 12.0-V battery with a 0.0100-Ω internal resistance. If the battery connections are corroded and add 0.0900 Ω to the circuit. (Significant problems are caused by even small amounts of unwanted resistance in low-voltage, high-current applications.)(a) What is the current to the motor? (b) What voltage is applied to it? (c) What power is supplied to the motor?

###### FREE Expert Solution

Let the added resistance due to the corrosion be r1 is added. The current in the motor will be calculated as:

$\overline{){\mathbf{i}}{\mathbf{=}}\frac{\mathbf{\epsilon }}{\mathbf{R}\mathbf{+}\mathbf{r}\mathbf{+}{\mathbf{r}}_{\mathbf{1}}}}$

Voltage in the motor is expressed as:

$\overline{){\mathbf{V}}{\mathbf{=}}{\mathbf{i}}{\mathbf{R}}}$

Power is:

$\overline{){\mathbf{P}}{\mathbf{=}}{{\mathbf{i}}}^{{\mathbf{2}}}{\mathbf{R}}}$

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###### Problem Details

An automobile starter motor has an equivalent resistance of 0.0500 Ω and is supplied by a 12.0-V battery with a 0.0100-Ω internal resistance. If the battery connections are corroded and add 0.0900 Ω to the circuit. (Significant problems are caused by even small amounts of unwanted resistance in low-voltage, high-current applications.)

(a) What is the current to the motor?

(b) What voltage is applied to it?

(c) What power is supplied to the motor?